A statement from Madame Tussauds has been causing offence. The world's most famous collection of wickless candles announced: "We proactively encourage our visitors to interact with the waxworks should they so choose." No surprise that caused a stink, you're probably thinking. It's one of the most horrible sentences ever written. Why "proactively encourage" rather than "actively encourage" or just "encourage"? And what's that "should they so choose" doing there? If the visitors have so chosen, you're not encouraging them actively, proactively or otherwise, you're just letting them. That's the opposite of proactive: antipassive, presumably.

That's not why the statement is controversial though. It's because it defends tourists' right to stand beside a waxwork of Adolf Hitler doing Nazi salutes. An Israeli couple visiting the attraction ("attraction" is the word people use, right? Rather than "museum" or "racket". "Attraction" as in: "I really can't understand the…") were horrified both by the fact that there was a likeness of Hitler at all and that people were posing next to it doing fascist gestures. It was their complaint that elicited Tussauds' assault on the English language.

I'm not doubting for a moment the sincerity of the couple's distress. Well, all right, maybe just for a moment. There. It's over now and I've concluded they were properly upset. God knows, they'd just queued up to get into Madame Tussauds on a summer's day in London. They'd be tired, hot and £57.60 poorer. Of course they'll have been disgusted and horrified by what they saw inside. And then, to make matters worse, they notice people saluting next to Hitler's waxwork.

They wrote in their complaint: "We are the grandchildren of concentration camp survivors – the very people that Hitler tried to kill." Of course I can understand why they might consider tourists frolicking with his likeness to be a display of inappropriate levity. But their complaint went further than that, claiming that the Nazi gestures and crying of "Heil Hitler!" were "an unequivocal demonstration of antisemitism and bigotry".

I just don't think that's true. The couple actually photographed two young tourists heil-Hitlering next to the waxwork and one of them is doing the moustache with her other hand. I'm pretty sure that neo-Nazis don't do the moustache. They certainly didn't do the moustache at the Nuremberg rallies. What those kids in the picture are doing, I'm willing to bet, is taking the piss out of Hitler.

That's why I think it's a shame that Tussauds' reasonable response created a stir. Having apologised for any offence caused, Tussauds continued on the subject of interacting with the waxworks: "We absolutely defend the right of our visitors to make such choices for themselves, as long as they behave themselves responsibly." The repeated "themselves" isn't great but I completely approve of the sentiment. And I was disappointed that Lord Janner, chairman of the Holocaust Educational Trust, did not. He said: "I'm appalled at Madame Tussauds' insensitive comments defending such activity, as surely they have a responsibility to ensure visitors behave appropriately and respectfully at their museum."

Respectfully of what? Hitler? Does he think the girl shouldn't have done the moustache? Or does he think Madame Tussauds should ban a specific arm gesture when people are standing next to the Hitler waxwork? Or ban it in general so they can't do it next to Margaret Thatcher, Sting or Timmy Mallett either? After all, Germany has banned it throughout the whole country. What a stereotypically German solution to a stereotypically German problem. Given the chance, they'd ban authoritarianism.

When you ban something like this, you only dignify it with significance. You spoil the harmless piss-takers' harmless fun and you justify fascists in their feelings of oppression. You take a stupid gesture out of the realm of mockery and you give it illicit cachet. Whereas, in general, freedom engenders freedom. If you let people do what they like, human decency usually prevails. Anyone doing a Nazi salute and saying "Heil Hitler" for reasons other than a joke is unlikely to garner sympathy. There are always evil, oppressive forces at work on any society but they'll be found wanting in guile if they come at us goose-stepping and shouting "Sieg Heil!" for a second time. The only thing that could make that seem attractive or worth following, even to an idiot, is if it were banned.

It appears that Lord Janner and I fundamentally disagree on the importance of solemnity where discussion of Hitler is concerned. He seems to think that, since the murder of millions isn't funny, there is nothing to laugh at about the Nazis. I think that's nonsense. One of the attributes of the British of which I am most proud is our reaction to Hitler and his regime: both during the war and subsequently, we've always found them so funny, so ridiculous.

It beggars belief, it is positively hilarious, that a whole country fell so completely in thrall to a posturing little prick like Hitler, who needed no help from our propagandists to look daft. There he is in the footage, making his speeches, all weedy and sweaty and cross – and there are the thousands of people cheering him as if he's Elvis. It makes you laugh like Titania falling in love with Bottom.

It's perfectly possible – and important to our understanding of the human condition – to find that amusing, to laugh at the goose-stepping, the shouting and the pomposity, while simultaneously holding in our heads the tragic murderous consequences of Nazi power. That's what makes the joke bite and also what reminds us that the massive disaster was human.

Churchill got this. It was no accident that he insisted on mispronouncing Nazi as "nar-zee" and referred disparagingly to "Corporal Hitler". He wasn't underestimating the scale of the threat or making light of people's suffering. But he knew it was vital to remember that the evil men who were jeopardising civilisation were also risible little twerps.

Many second world war veterans were accustomed to joking about Hitler. Spike Milligan and his contemporaries founded a comic tradition of making fun of the Nazis which has given us Peter Sellers's performance in Dr Strangelove, "The Germans" episode of Fawlty Towers, Dad's Army, 'Allo 'Allo!, endless YouTube resubtitlings of Downfall and Prince Harry's party gear. Just because the wartime generation has largely gone, we mustn't lose our comic nerve. While we must never forget the scale and severity of Hitler's crimes, we will have lost something precious if we start taking him seriously.